1. Field of the Invention
This invention relates to a method of driving an ink jet head for discharging ink in accordance with an ink jet process and effecting recording on a recording medium, an ink jet head and an ink jet recording apparatus, and particularly to what utilizes heat energy to discharge ink.
“Recording” in the present invention means not only imparting images having meanings such as characters and figures, but also imparting images having no meaning such as patterns.
2. Related Background Art
In recent years, numerous recording apparatuses have come to be used as apparatuses such as a printer for effecting recording on recording mediums such as paper, yarn, fiber, cloth, metals, plastics, glass, wood and ceramics, a copying machine, a facsimile apparatus having a communication system, and a word processor having a printer portion, and further a recording apparatus compoundly combined with various processing apparatuses. High-speed recording, high resolution, a high quality of image, low noise, etc. are required of these recording apparatuses. An ink jet recording apparatus may be mentioned as a recording apparatus meeting such requirements. The ink jet recording apparatus uses an ink jet head having a discharge port, discharges ink (recording liquid) droplets from the discharge port and makes them adhere to a recording medium to thereby effect recording. In the ink jet recording apparatus, the ink jet head and the recording medium are in non-contact with each other and therefore, very stable recorded images or the like can be obtained.
Among such ink jet heads, an ink jet head utilizing heat energy to discharge ink has the advantages that a number of discharge ports can be arranged highly densely and therefore recording of high resolution can be effected, and that it is easy to make the head compact.
In the conventional ink jet head utilizing heat energy, a plurality of heat generating resistance members are arranged in the form of a row on a base member of silicon or the like to thereby achieve high density, and a construction having a common heat accumulation layer and electrical insulating film to the plurality of heat generating resistance members is popular (Japanese Patent Application Laid-open No. 2001-171127 and Japanese Patent Application Laid-open No. 2002-011886).
FIG. 14 of the accompanying drawings shows a typical cross-sectional view of the conventional ink jet head utilizing heat energy in the portion of a heat generating resistance member thereof.
As shown in FIG. 14, the ink jet head 100 has a base member 120 formed with a heat generating resistance member (heater) 123, and a nozzle material 110 joined onto the base member 120. The base member 120 has, on the surface of a substrate 121 formed of silicon, a heat accumulation layer 122 constituted by a plurality of layers such as thermally oxidated film, a heat generating resistance member 123 partly formed on the heat accumulation layer 122, electrode wires 124, 125 for supplying electric power to the heat generating resistance member 123, electrical insulating film 126 formed so as to cover the heat generating resistance member 123 and the heat accumulation layer 122, and anti-cavitation film 127 consisting of Ta and formed on the electrical insulating film 126. The electrical insulating film 126 and the anti-cavitation film 127 together constitute protection film 128. The nozzle material 110 is joined to the base 120 to thereby form a liquid path having an ink chamber 112 above the heat generating resistance member 123. Also, the nozzle material 110 has a discharge port 111 formed at a location opposed to the heat generating resistance member 123.
The ink chamber 112 is filled with ink and in this state, a voltage is applied to the heat generating resistance member 123 through the electrode wires 124 and 125, whereby the heat generating resistance member 123 generates heat. By the heat generation of the heat generating resistance member 123, the ink in the ink chamber 112 is suddenly heated and film-boils. Thereby, a bubble is produced in the ink, and by pressure based on the growth of the bubble, the ink is discharged from the discharge port 111.
In order to efficiently transmit the heat energy generated by the heat generating resistance member 123 to the ink, various contrivances have heretofore been proposed about the film construction of the base member 120.
Reference is now made to FIG. 15 of the accompanying drawings to describe the principle of heat transmission by the heat generation of the heat generating resistance member 123. In FIG. 15, the heat generating resistance member 123 is electrically energized, whereby a quantity of heat Q is applied. The quantity of heat Q is diffused to above and below the heat generating resistance member 123 and becomes Q1 and Q2. The quantity of heat Q1 diffused to above is transmitted to the ink 130 on the protection film 128. Thereby, a bubble 131 is produced in the ink 130, and discharge is effected as described above.